It's a question that's had a lot of relevance for me recently - since the beginning of the year I've been interviewing (unsuccessfullly) for a post at Google, freelancing, and wondering what direction to try and take my skillset in.
It's an ongoing problem in the tech industry - for most jobs, the jobspec requires "strong skills" in two or three seperate (sometimes not very closely related) skills. And you have a choice when you're looking for roles; either try and find the elusive "perfect match", or hope that an employer will accept background or comparable skills as an equivalent.
And there's a counterpart to this when you try and decide how to develop your skillset - do you dedicate your energies towards a specific area ("Linux Sysadmin", "PHP web developer" or some such) or do you try and be a generalist? In the first case, you risk missing the skills employers want by reason of being too narrow, and in the latter you're either assumed to be "jack of all trades and master of none" or take the risk that, even if you have skills in a specific area, you're not used them recently enough in a professional context, and they're assumed to be "out of date".
So, really, I think you just have to take things as they come - take the opportunity to learn whatever skills your employer sends your way, and keep "playing" with whichever technologies take your interest in your "downtime". Recently I've had a bit of luck in that area - working for an employer that initially took me on as a freelance web developper, but then realised that they could throw most tech tasks at me and I'd be able to take them on. As such I've been doing everything from building network cables and servers, to implementing version control, system backups and mail-scanning - all useful tools to add to my arsenal.
Unfortunately the job's over the far side of London from where I live, so the commute's been seriously cutting into my downtime.
Of course I've been bringing these skills home with me, and from what I've learned or seen at work I've moved all of my own servers over to debian-testing (sarge), installed the backup tool at home, and set up jobs to monitor package update availability, and updated my apache servers to the latest available package. And, since it's been due to contributions from the community (on various websites) that I've been able to get everything done fairly smoothly, I'll be putting a few documents of my own on this site shortly. To some extent this will change the focus of this site a bit, but I think it's better to adapt the site than to let it fade.